U.S. patent number 4,817,447 [Application Number 07/063,641] was granted by the patent office on 1989-04-04 for weather resistance tester.
This patent grant is currently assigned to Dainippon Plastics Co., Ltd., Iwasaki Electric Co., Ltd. Invention is credited to Teruo Iwanaga, Yoshio Kashima, Hirofumi Kinugasa, Yasuo Yoshida.
United States Patent |
4,817,447 |
Kashima , et al. |
April 4, 1989 |
**Please see images for:
( Certificate of Correction ) ** |
Weather resistance tester
Abstract
A weather resistance tester comprising: (a) a U.V. radiation
source, (b) a reflector, (c) a shield panel provided in the opening
of the reflector and closing the opening for transmitting U.V.
radiation therethrough and substantially blocking water vapor, (d)
a sample support, (e) temperature adjusting device, (f) a
compartment having accommodated therein the above elements (a)-(e),
(g) a recycling duct provided with a heat exchanger and blower, (h)
a humidifier and (i) a control device for giving operational
instructions to maintain a sample on the sample support at a
predetermined temperature while the lamp is on and to subject the
sample to a condensation condition while the lamp is off.
Inventors: |
Kashima; Yoshio (Kasukabe,
JP), Kinugasa; Hirofumi (Matsudo, JP),
Yoshida; Yasuo (Gyoda, JP), Iwanaga; Teruo
(Gyoda, JP) |
Assignee: |
Dainippon Plastics Co., Ltd.
(Osaka, JP)
Iwasaki Electric Co., Ltd (Tokyo, JP)
|
Family
ID: |
15308592 |
Appl.
No.: |
07/063,641 |
Filed: |
June 17, 1987 |
Foreign Application Priority Data
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Jun 17, 1986 [JP] |
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61-142153 |
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Current U.S.
Class: |
73/865.6;
374/57 |
Current CPC
Class: |
G01N
17/00 (20130101); G01N 17/004 (20130101) |
Current International
Class: |
G01N
17/00 (20060101); G01N 017/00 () |
Field of
Search: |
;73/865.6 ;374/57 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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13451 |
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Apr 1980 |
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JP |
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18743 |
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Apr 1983 |
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JP |
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117128 |
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Jun 1985 |
|
JP |
|
117129 |
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Jun 1985 |
|
JP |
|
Primary Examiner: Noland; Tom
Attorney, Agent or Firm: Cohen, Pontani & Lieberman
Claims
What is claimed is:
1. A weather resistance tester comprising:
(a) a U.V. radiation source comprising a lamp for generating U.V.
radiation;
(b) a reflector having the U.V. source accommodated therein and an
opening at a lower portion thereof for permitting the lamp to
project U.V. radiation downward through the opening;
(c) a shield panel provided in the opening of the reflector and
closing the opening for transmitting U.V. radiation therethrough
and substantially blocking water vapor therefrom;
(d) a sample support disposed below the opening;
(e) means for adjusting the temperature in operative relation with
the sample support;
(f) a compartment having accommodated therein the U.V. source, the
reflector, the shield panel, the sample support and the temperature
adjusting means;
(g) a recycling duct having an intake portion and an outlet portion
connected to the compartment and provided with a heat exchanger and
means for blowing air;
(h) a humidifier in operative relation with the sample support for
providing a condensation condition therearound; and
(i) control means for giving operational instructions to the U.V.
source, the temperature adjusting means, the heat exchanger, the
blower means and the humidifier to maintain a sample on the sample
support at a predetermined temperature while the lamp is on and to
subject the sample to a condensation condition while the lamp is
off.
2. The tester as defined in claim 1 wherein the shield panel is a
thin plate of quartz glass.
3. A tester as defined in claim 2, wherein the thin plate of quartz
glass is 1 to 4 mm in thickness.
4. The tester as defined in claim 1, wherein the shield panel
comprises a thin plate of quartz glass having a thin plate of
infrared absorption glass superposed thereon.
5. The tester as defined in claim 1, wherein the humidifier
comprises a water tank, a heater provided within the tank and
operable in response to an instruction from the control means, and
a water feeder for supplying water to the water tank and for
maintaining the water at a constant level within the tank.
6. The tester as defined in claim 1, wherein the humidifier is
disposed within the compartment and comprises a water tank, a
heater provided within the tank and operable in response to an
instruction from the control means, a water feeder for supplying a
water to the tank and for maintaining the water at a constant level
within the tank, and a humidifiying duct extending from the water
tank toward the sample support for guiding water vapor produced in
the water tank to a location close to the sample on the sample
support.
7. The tester as defined in claim 1, wherein the outlet portion of
the recycling duct comprises an air recycling nozzle extending from
a wall of the compartment toward the sample support for guiding
recycle air to around the sample on the sample support.
8. The tester as defined in claim 1, wherein the temperature
adjusting means comprises a temperature sensor mounted on an upper
portion of the sample support for feeding a temperature signal to
the control means, and a cooling water channel provided beneath the
sample support.
9. The tester as defined in claim 1, wherein the heat exchanger
comprises a heater and a refrigeration cycle evaporator.
10. The tester as defined in claim 1, wherein the lamp is a metal
halide lamp for emitting U.V. radiation substantially in the
wavelength range of from 300 to 400 nm.
11. The tester as defined in claim 1, wherein the reflector is
substantially dome-shaped.
12. The tester as defined in claim 1, wherein the reflector
comprises a substantially dome-shaped main reflecting member having
two long sides and two short sides and an auxiliary reflecting
member extending from the lower peripheral edge of the main
reflecting member downward toward the sample support.
13. The tester as defined in claim 12, wherein the auxiliary
reflecting member extends from the lower peripheral edge of the
main reflecting member vertically downward at an angle with the
vertical.
14. The tester as defined in claim 13, wherein the auxiliary
reflecting member extends downwardly outward at an angle of 5 to 35
degrees with the vertical.
15. The tester as defined in claim 12, wherein the lamp is in the
form of an elongated tube disposed horizontally, and the main
reflecting member is elongated along the lamp and substantially
parabolic in cross section, the auxiliary reflecting member
comprising two lengthwise reflecting plates respectively extending
downward from the lower ends of the two long sides of the main
reflecting member.
16. The tester as defined in claim 15, wherein the reflecting
surface of the main reflecting member is a semi-diffusion
surface.
17. The tester as defined in claim 12, wherein the lamp is in the
form of an elongated tube disposed horizontally, and the main
reflecting member is elongated along the lamp and substantially
parabolic in cross section, the auxiliary reflecting member
comprising two widthwise reflecting plates respectively extending
downward from the lower ends of the two short sides of the main
reflecting member.
18. The tester as defined in claim 12, wherein the lamp is in the
form of an elongated tube disposed horizontally, and the main
reflecting member is elongated along the lamp and substantially
parabolic in cross section, the auxiliary reflecting member
comprising two lengthwise reflecting plates and two widthwise
reflecting plates extending downward from the lower ends of the two
long sides of the main reflecting member and from the lower ends of
the two short sides thereof respectively.
19. The tester as defined in claim 18, wherein each pair of the
lengthwise reflecting plates extend from the lower end of the main
reflecting member vertically downward at an angle with the
vertical.
20. The tester as defined in claim 19, wherein each widthwise
reflecting plate comprises an upper widthwise segment extending
from the short side lower end of the main reflecting member
downwardly outward at an angle with the vertical, and a lower
widthwise segment extending from the lower end of the upper segment
downwardly outward at a smaller angle than the upper segment with
respect to the vertical.
21. The tester as defined in claim 20, wherein each lengthwise
reflecting plate extends from the long side lower end of the main
reflecting member downwardly outward at an angle of 5 to 11 degrees
with the vertical, the upper widthwise segment extending from the
short side lower end of the main reflecting member downwardly
outward at angle of 12 to 20 degrees with the vertical, the lower
widthwise segment extending from the lower end of the upper segment
downwardly outward at an angle of 5 to 11 degrees with the
vertical.
22. The tester as defined in claim 21, wherein each lengthwise
reflecting plate extends from the long side lower end of the main
reflecting member downwardly outward at an angle of about 8 degrees
with the vertical, the upper widthwise segment extending from the
short side lower end of the main reflecting member downwardly
outward at an angle of about 15 degrees with the vertical, the
lower widthwise segment extending from the lower end of the upper
segment downwardly outward at angle of about 8 degrees with the
vertical.
23. The tester as defined in claim 18 wherein the lengthwise
reflecting plates extend from the long side lower end of the main
reflecting member downwardly outward at an angle of 5 to 11 degrees
with the vertical, and the widthwise reflecting plates extend from
the short side lower ends of the main reflecting member downwardly
outward at an angle of 12 to 35 degrees with the vertical.
Description
FIELD OF THE INVENTION
The present invention relates to weather resistance testers, and
more particularly to an apparatus for testing plastics, coating
compositions, inks, pigments, fibers, etc. for weather resistance
under conditions involving a condensation condition.
RELATED ART STATEMENT
Plastic materials, coating compositions and the like have
heretofore been tested for weather resistance (lightfastness)
generally by testers according to JIS B 7751-7754. Such testers
usually include a carbon arc lamp, xenon arc lamp or like light
source for irradiating samples with its light to perform
accelerated weather resistance tests.
With these testers, however, the intensity of ultraviolet (U.V.)
rays for irradiating the sample is generally about 6 mW per square
centimeter of the surface to be exposed, such that the tester
requires at least several hundreds of hours for determining U.V.
deterioration characteristics corresponding to those resulting from
a one-year exposure to sunlight.
Since it is common practice to test all the samples of individual
lots, the testing procedure also requires a long period of time for
determining the characteristics and evaluating the results and
therefore involves the problem of extremely low efficiency.
This problem will be overcome, for example, by exposing the samples
of individual lots to very intensive U.V. rays before testing for
weather resistance to effect accelerated U.V. deterioration,
selecting the samples to be tested from among the exposed samples
according to the degree of deterioration and thereafter testing
only the selected samples by the weather resistance tester. This
eliminates the need to test all the samples by weathering, leading
to a greatly improved testing efficiency.
We have already proposed an apparatus for pretesting the samples of
individual lots before the usual weathering test, by exposing the
samples to U.V. rays having a high intensity, for example, of at
least about 50 mW/cm.sup.2 with a metal halide lamp, whereby the
samples can be checked for U.V. deterioration within a very short
period of time, e.g., within up to 1/10 of the time conventionally
required (see Unexamined Japanese Patent Publications SHO 60-117128
and SHO 60-117129). The pretesting apparatus is of course usable
also as a weather resistance tester.
It is desired that the weathering test for plastics, coating
compositions or like materials be conducted, to the greatest
possible extent, under the same physical conditions as those to
which the material is subjected during actual use. In the
nighttime, the material in use is not only exposed to low
temperatures due to the absence of sunlight but is also likely to
be exposed to the condensate of water vapor.
If the conditions for the weathering test or pretesting therefor
involve such a condensation condition, the result obtained will
serve to provide a commercial product of improved quality as
demanded by the community.
Examined Japanese Patent Publication SHO 55-13541, for example,
proposes to dip the sample in water in order to subject the sample
to such a condensation condition. The dipping method nevertheless
in no way realizes the actual state of condensation, nor can it be
a substitute therefor.
In view of this drawback, we thought it useful to adjust the
temperature of the sample and the temperature and humidity of the
air surrounding the sample in subjecting the sample to the actual
condensation condition, and investigated whether our proposed
apparatus for weathering test or pretesting could be so adapted
without impairing the acceleration characteristics of the
weathering test.
The condensation of water vapor is dependent generally on the
temperature and the humidity. Our investigations have revealed that
even if a condensate of water vapor can be deposited on the sample,
some components of the apparatus other than the sample are then
likely to be under the same temperature and humidity conditions as
the sample, consequently becoming fogged up on condensation or
locally permitting deposition of dust or the like thereon due to
drops of water condensate. Thus, the condensation of water vapor is
liable to produce various objections.
Especially when the cooling water jacket or reflector (mirror) for
the metal halide lamp is subjected to condensation, there arises
the problem that the sample will not be fully exposed to the U.V.
radiation (smaller than 400 nm in wavelength, 10 to 30% of the
total quantity of light) which is essential to the acceleration of
weathering). While the weather resistance tester disclosed in
Patent Publication No. SHO 55-13541 mentioned above has
incorporated therein a xenon lamp which is originally low in the
intensity of irradiating U.V. radiation (less than 400 nm in
wavelength, 3.25% of the total quantity of light), the tester is
totally unable to perform weathering tests in any accelerated mode
if locally exposed to the condensate of water.
SUMMARY OF THE INVENTION
The present invention provides a weather resistance tester
comprising:
(a) a U.V. radiation source comprising a lamp for generating U.V.
radiation,
(b) a reflector having the U.V. source accommodated therein and an
opening at its lower portion for permitting the lamp to project
U.V. radiation downward through the opening,
(c) a shield panel provided in the opening of the reflector and
closing the opening for transmitting U.V. radiation therethrough
and substantially blocking water vapor,
(d) a sample support disposed below the opening,
(e) temperature adjusting means provided for the sample
support,
(f) a compartment having accommodated therein the U.V. source, the
reflector, the shield panel, the sample support and the temperature
adjusting means,
(g) a duct having an intake portion and an outlet portion connected
to the compartment and provided with a heat exchanger and means for
blowing air,
(h) a humidifier in operative relation with the sample support for
providing a condensation condition therearound; and
(i) control means for giving operational instructions to the U.V.
source, the temperature adjusting means, the heat exchanger, the
blower means and the humidifier to maintain a sample on the sample
support at a predetermined temperature while the lamp is on and to
subject the sample to a condensation condition while the lamp is
off.
According to the present invention, the temperature adjusting means
provided for the sample support and the humidifier disposed in the
duct or in the compartment are operated under a specified condition
through the control means to lower the temperature of the sample to
a level not higher than the dew point while the lamp is off and to
thereby subject the sample to a nearly natural condensation
condition.
As another important feature of the present invention, the opening
at the lower portion of the reflector is closed with a shield panel
which permits passage of U.V. radiation therethrough but
substantially blocks water vapor to partition the interior of the
reflector from the other compartment portion wherein the sample is
positioned. This prevents a specified portion of the tester from
the condensation of water vapor that would be objectionable to the
projection of U.V rays, further diminishing the pace to be
controlled in temperature and humidity to assure the desired
control with greater ease and improved reliability.
Since the shield panel is disposed in the same space as the sample
to be exposed to water condensate, there still remains the
likelihood that water vapor will condense on the shield panel.
However, the sample support is provided with the temperature
adjusting means as stated above, by which the temperature of the
sample support only is directly adjustable to lower the temperature
of the sample alone to the dew point or lower. This further reduces
the likelihood of condensation on the shield panel.
When the humidifier included in the present tester is provided with
a nozzle-shaped humidifying duct for guiding water vapor to a
position around the sample, the shield panel can be precluded from
condensation more effectively.
The shield panel used in the present invention for transmitting
U.V. radiation but substantially blocking water vapor means a plate
which is capable of efficiently passing therethrough the U.V. rays
required for weather resistance tests and further capable of
blocking water vapor (moisture).
Preferably, the shield panel is a plate, such as a thin plate of
quartz glass of 1 to 4 mm in thickness, which is capable of
efficiently transmitting U.V. rays, chiefly 300 to 400 nm in
wavelength, and capable of efficiently blocking rays in the
wavelength regions of less than 300 nm and over 400 nm.
The shield panel of the present invention may comprise a plurality
of superposed plates to obtain the desired transmission
characteristics when so required. For example, a thin plate of
infrared absorption glass may be superposed on the above-mentioned
thin plate of quartz glass for converting the infrared rays from
the lamp to heat on absorption so as to effectively preclude
condensation on the shield panel itself.
Further according to the present invention, the sample can be
exposed to U.V. radiation with remarkably improved uniformity
merely by attaching a specified auxiliary reflector to the
reflector. This obviates the manual procedure, such as replacement
of the sample, that would otherwise be needed.
For example, when the reflector used is dome-shaped (e.g.,
parabolic), the intensity of U.V. radiation irradiating the sample
(surface) tends to be higher at the central portion of the sample
and to be lower at the peripheral portion thereof. Especially when
a spot light source or linear (elongated) light source is used as
the lamp, the intensity of light on the sample surface involves
variations (i.e., low uniformity), consequently necessitating the
replacement of the sample to diminish variations in the test
result.
The sample can be exposed to the U.V. radiation with increased
uniformity by extending the main reflector partially or entirely
from its lower peripheral edge downward to provide an auxiliary
reflector so that the portion of the U.V. radiation which otherwise
uselessly impinges on the portion around the sample is
concentrically directed toward the peripheral portion of the
sample.
The angle of the auxiliary reflector thus provided is of extreme
importance. Preferably, the auxiliary reflector is vertical or
extends downwardly outward with respect to the vertical, more
preferably at an angle of 5 to 35 degrees with the vertical.
When the lamp is in the form of an elongated tube disposed
horizontally, a reflector assembly is desirable which comprises a
main reflector elongated along the lamp and substantially parabolic
in cross section, and an auxiliary reflector comprising two
lengthwise reflecting plates respectively extending downward from
the lower ends of the two long sides of the main reflector and/or
two widthwise reflecting plates respectively extending downward
from the lower ends of the two short sides of the main reflector.
Preferably the opposed reflecting plates in each pair extend
downward vertically or as inclined downwardly outward away from
each other at an angle with the vertical. Stated specifically, it
is preferred that the lengthwise reflecting plates extend
downwardly outward at an angle of 5 to 11 degrees with the vertical
and that the widthwise reflecting plates extend downwardly outward
at an angle of 12 to 35 degrees with the vertical.
The weather resistance tester embodying the present invention is
thus adapted to expose samples to a large quantity of light energy
(chiefly of U.V. energy) for causing accelerated weathering
deterioration within a shortened period of time under a
condensation condition which is given without impeding the
application of light energy. Moreover, the light energy can be
applied to the sample with improved uniformity for testing the
sample with improved precision. The present tester is therefore
well-suited for testing plastics, coating compositions, inks,
pigments, dyes, fibers, etc. for weather resistance or for
pretesting such materials before the weathering test.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 (A) and (B) are diagrams showing the construction of an
embodiment of the invention;
FIG. 2 is an enlarged fragmentary view showing the same;
FIGS. 3 to 7 are graphs showing variations in the color difference
or gloss of samples under varying conditions;
FIG. 8 is a graph showing the energy distributions of lamps and the
transmittance characteristics of a filter;
FIG. 9 is a diagram showing a cooling water circuit for the lamp
and sample support of the embodiment shown in FIGS. 1 and 2;
FIG. 10 is a diagram showing a temperature control circuit for the
embodiment;
FIG. 11 is a diagram showing a humidity control circuit for the
embodiment;
FIG. 12 is a timing chart showing exemplary operation modes of the
embodiment;
FIG. 13 is an enlarged fragmentary diagram showing another
embodiment of the invention; and
FIG. 14 is an enlarged fragmentary diagram showing the second
embodiment as it is seen from a different direction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The tester of the present invention includes a lamp serving as a
U.V. radiation source. Examples of useful lamps are a metal halide
lamp, carbon arc lamp, xenon arc lamp, U.V. fluorescent lamp,
sunlight lamp and the like, among which the metal halide lamp is
preferred.
The metal halide lamp comprises a light-emitting tube made of
quartz glass and having at least one pair of electrodes. The tube
has enclosed therein suitable quantities of mercury and rare gas,
and metal halides primarily including an iron halide or halides of
iron and tin. Examined Japanese Patent Publication SHO 58-18743
discloses specific examples of such metal halide lamps.
The metal halide lamp, when turned on, exhibits a nearly continuous
emission spectrum over the wavelength range of 300 to 400 nm as
seen in FIG. 8 in comparison with a mercury lamp. Thus, the metal
halide lamp has a distribution of considerably great optical
energies which are predominantly available over the wavelength
range of 300 to 400 nm. The lamp therefore gives samples a large
quantity of light energy which causes accelerated weathering
deterioration within a short period of time. More specifically
stated, the sample can be exposed to U.V. rays at a high intensity
of at least about 50 mW per square centimeter of the surface, with
the result that the deterioration characteristics of the sample can
be determined and evaluated within a greatly shortened period of
time, i.e., up to 1/10 the time conventionally needed as already
mentioned.
The metal halide lamp, nevertheless, invariably emits energy over
the wavelength regions other than 300 to 400 nm, whereas the
sunlight actually reaching the earth does not include U.V. rays of
less than about 300 nm. On the other hand, the rays exceeding 400
nm in wavelength include large quantities of visible rays and
infrared rays which thermally elevate the temperature of the sample
and are therefore undesirable. This gives rise to the necessity of
using a suitable filter in combination with the lamp to use the
wavelengths of about 300 to about 400 nm only for irradiation.
Examples of such filters are thin plates of low melting point soft
glass, more preferably those comprising 60 to 65% (by weight, the
same as hereinafter) of SiO.sub.2, 15 to 20% of Pb, 7 to 8% of Na,
7 to 8% of K, 1% of Co and 1% of Ni (e.g., Blue Filter (brand
name), product of Sankyo Denki Co., Ltd.). While such a filter
should be suitably used in combination with the metal halide lamp,
the filter, if merely disposed in the vicinity of the lamp, would
be immediately broken by the heat radiated by the lamp. In actual
use, therefore, the light-emitting tube is disposed in the center
of a cooling water jacket, with the filter provided inside the
jacket. Stated more specifically, the jacket may be in the form of
a double tube comprising an inner tube and an outer tube, and the
light-emitting tube is disposed inside the inner tube, with the
filter provided between, the inner and outer tubes, for passing
filter cooling water through the space between the inner and outer
tubes. The cooling water will of course also cool the
light-emitting tube.
For reference, Table 1 shows the influence of Blue Filter,
mentioned above, on the U.V. radiation from some light sources.
Each value listed is the intensity (W) of U.V. radiation from the
light source The input to the light source is 100 W.
TABLE 1 ______________________________________ Wavelengths 300-400
nm Light source Without filter With filter
______________________________________ Metal halide lamp 18.9 11.8
Mercury lamp 10.0 5.8 Xenon lamp 7.3 3.5
______________________________________
The present invention will be described below in greater detail
with reference to the embodiments shown in the drawings. The
invention, however, is in no way limited by these embodiments.
Referring to FIGS. 1, 2 and 9 to 11, the weather resistance tester
T shown mainly comprises a tester main body 3 having a U.V.
irradiation compartment 2, a light source device 4 serving as a
U.V. radiation source and provided in the interior upper portion of
the compartment 2, a sample support 7 disposed below the light
source device 4, a temperature adjustment recycling duct 18, a
humidifier 12, a control unit 30 and a heat exchanger 36.
The light source device 4, which is shown in greater detail in FIG.
2, comprises a substantially dome-shaped collimating main reflector
33, an auxiliary reflector 33a, a metal halide lamp 1 and a cooling
water jacket 32 therefor which are accommodated inside the assembly
of the reflectors 33, 33a, and a quartz glass plate 34 serving as a
shield panel and closing an opening at the lower portion of the
reflector assembly for partitioning the interior of the reflector
assembly from the other portion of the U.V. irradiation compartment
2. The shield plate, i.e.,the quartz glass plate 34 is capable of
transmitting U.V. radiation but substantially blocks water vapor.
FIG. 2 further shows a fastener 39 for the shield panel and seal
packings 40.
The sample support 7 is provided with temperature adjusting means
6, which comprises a temperature sensor 17 (see FIG. 1 (A)) mounted
on an upper portion of the sample support 7 for feeding a
temperature signal to the control unit 30, and a cooling water
recycling channel 31 provided beneath the support 7. The water
channel 31 is provided with a heat exchanger 42 (FIG. 9) and a
water recycling pump (not shown) which are given an operation
instruction by the control unit 30. Indicated at 41 is a heat
insulator.
Through the recycling duct 18, the air within the compartment 2 is
partly withdrawn therefrom through intake openings 35 (see FIG. 1
(B)) of the compartment, then passed through the heat exchanger 36
and the humidifier 12 and introduced into the compartment again
from a nozzle-shaped outlet 25 above the sample support 7.
Indicated at 10 is a blower for the recycling duct 18. The heat
exchanger 36 comprises an upstream cooling unit 9 comprising an
evaporator of a refrigeration system, and a downstream heating unit
8 comprising a heater.
The humidifier 12 comprises a water tank 37, a heater 11 provided
within the tank 37, a water feeder 47 (FIG. 11) for supplying water
to the water tank 37 and maintaining the water at a constant level
within the tank, and a humidity sensor 5. The water vapor produced
is guided to a location close to a sample S on the support 7 by a
humidifying duct 38 having a nozzle-shaped forward end.
FIG. 1 further shows a cooler 13 for the metal halide lamp 1, a
water container 14, a stabilizer 15 for the lamp 1, a refrigerator
16 for the heat exchanger 36, a lamp-on timer 19, a condensation
timer 20, a humidity controller 21, a temperature controller 22, an
overall testing time setting timer 23 and a U.V. radiation
intensity meter 24. FIG. 9 shows a solenoid valve 43 which is
energized when the lamp 1 is turned on, a solenoid valve 44 to be
energized for condensation, a flow rate sensor 45 and a water drain
46.
The control unit 30 gives an operation instruction to each of the
metal halide lamp 1, blower 10, heat exchanger 36, humidifier 12
and heat exchanger 42. First, the U.V. radiation source, i.e., the
metal halide lamp 1 is turned on, whereby the sample S placed on
the support 7 is exposed to U.V. radiation for a specified period
of time (about 8 hours). During the exposure, the heat exchanger 36
and the blower 10 operate in response to a signal from the
temperature sensor 17, maintaining the sample S at a specified
temperature (40.degree. to 100.degree. C..+-.1.0.degree. C.).
Subsequently, the lamp 1 is turned off, terminating the U.V.
irradiation. In response to signals from the temperature sensor 17
and the humidity sensor 5, the temperature adjusting means 6 and
the humidifier 12 are given on-off instructions to lower the
temperature of the sample S to a level not higher than the dew
point and to supply hot humid air to the sample S via the recycling
duct 18, permitting condensation of water vapor. (Usually, the air
to be recycled has its temperature set to a level at least
5.degree. C. higher than the temperature of the sample and has its
humidity adjusted to at least 80%.) After this state has been
maintained for a predetermined period of time (about 4 hours), the
sample S is irradiated with U.V. radiation again in the same manner
above. The cycle described is repeated (see FIG. 12 (II)).
Thus, the sample S can be subjected to a weathering test or
pretested therefor within a greatly shortened period of time. Since
the weather resistance test or pretest is conducted under
conditions involving condensation closely resembling the
condensation actually occurring during nighttime, the test can be
carried out under nearly natural conditions. With the shield panel
34 of the light source device 4 closing the interior of the
assembly of the reflectors 33, 33a, the cooling water jacket 32 or
the specular surfaces of the reflectors 33, 33a are unlikely to
become fogged up, permitting the U.V. radiation to irradiate the
sample S as desired and assuring the weathering test or pretest
within a short period of time.
If the assembly of reflectors 33, 33a (i.e. the lamphouse) were not
closed with the shield panel 34, problems would be encountered as
will be described below in detail. While the cooling water jacket
32 or the specular surfaces of the reflectors 33, 33a fog up, the
interior atmosphere of the reflector assembly becomes hot and humid
(30.degree. to 80.degree. C. in temperature, 60 to 90% in
humidity), causing corrosion to the metal materials other than
stainless steel inside the reflector assembly and possibly
rendering the tester unusable in about a half a year. It is
especially likely that the aluminum material subjected to anodic
oxidation treatment and used for the reflectors 33, 33a will become
corroded to result in a reduction and variations in the intensity
of the irradiating U.V. radiation. While the reflector assembly
includes wiring for the application of a high voltage of 1000 V and
pulse voltage of about 800 V to light up the lamp, the
high-temperature high-humidity condition is liable to impair the
insulation for the wiring.
Depending on the instruction of the control unit 30, the lamp can
be held on continuously as shown in FIG. 12 (I) or held off to
provide a condensation-free cessation period as illustrated in FIG.
12 (III).
The compartment area surrounding the sample S would be uselessly
irradiated with a portion of the U.V. radiation if the main
reflector 33 only is used, whereas the auxiliary reflector 33a
collectively directs the radiation portion toward the peripheral
portion of the sample S so as to expose the sample to the U.V.
radiation with higher uniformity (uniformity on the surface of the
sample, as expressed by minimum irradiation intensity/maximum
irradiation intensity.times.100), thereby ensuring weathering tests
with improved reliability and higher reproducibility. Specifically
stated, the auxiliary reflector 33a comprises a pair of lengthwise
reflecting plates 33a parallel with a vertical plane through the
axis of the metal halide lamp 1, and a pair of widthwise reflecting
plates 33b (see FIG. 1 (B)) perpendicular to the plates 33a.
The opposed auxiliary reflecting plates in each pair, although
vertical in the above embodiment, may extend downwardly outward
away from each other at an angle with the vertical. For example,
FIGS. 13 and 14 show an auxiliary reflector which comprises a pair
of lengthwise reflecting plates 133a and a pair of widthwise
reflecting plates 133b. Each widthwise reflecting plate 133b
further comprises an upper segment 133bu and a lower segment 133bd
which is inclined at a smaller angle than the upper segment 133bu
with respect to the vertical. Thus, the lengthwise reflecting
plates 133a, as well as the widthwise reflecting plates 133b, are
inclined downwardly outward away from each other, with the result
that even if some U.V. rays are projected around a sample 100S,
U.V. rays are diffused over the peripheral portion of the sample
100S, with concentrated irradiation of the central portion thereof
avoided, permitting the sample to be irradiated with the U.V.
radiation with improved uniformity. In the case of the embodiment
of FIGS. 13 and 14, the main reflector 133 is further sandblasted
(No. 60) to provide a semidiffusion surface and obviate
concentration of the U.V. radiation on the central portion of the
sample 100S.
For reference, given below are the specifications of the reflectors
of FIGS. 13 and 14, and the U.V. irradiation data as to the
illustrated embodiment.
______________________________________ .alpha.: 8 deg x: 50 mm q:
50 mm t: 240 mm .beta.: 15 deg y: 55 mm r: 88 mm u: 101 mm .gamma.:
8 deg z: 400 mm s: 155 mm v: 45 mm w: 15 mm
______________________________________
Emission length of metal halide lamp 101: 500 mm
Average intensity of U.V. irradiation: 100 mW/cm.sup.2
Uniformity: 90%
As another embodiment, unlike the first embodiment of FIGS. 1 and
2, the humidifier can alternatively be disposed within the
recycling duct. The humidifier is then positioned downstream from
the heat exchangers (for heating and cooling). It is further
possible to conduct weathering tests under different conditions,
e.g. with addition of sulfurous acid gas, ozone or the like to the
air to be recycled.
Test examples are given below, in which several kinds of samples
were tested for weathering resistance using the tester of FIGS. 1
and 2 according to the invention and a commercial tester to
determine U.V. deterioration under conditions involving
condensation.
Testers and Test Conditions
(1) Tester of the invention (shown in FIGS. 1 and 2)
Lamp: Metal halide lamp, 4 kW.
Shield panel: Quartz glass (transmitting at least 90% U.V rays,
300-400 nm).
Radiation wavelength: 300-400 nm (see FIG. 8 for details).
Maximum temperature of sample surface: Up to 65.degree. C.
Black panel temperature: 63.+-.3.degree. C.
U.V. radiation intensity on sample surface: 100.+-.5
mW/cm.sup.2.
Condensation cycle: The cycle of 8-hour U.V. irradiation and 4-hour
condensation was repeated. Condensation was effected at sample
temp. of 30.degree. C., recycling air at temp. of at least
35.degree. C. and humidity of at least 80%.
(2) Commercial tester (of prior art)
Brand name: Eye Super UV Tester, product of Iwasaki Electric Co.,
Ltd.
Lamp: Metal halide lamp, 4 kW.
Radiation wavelength: 300-400 nm (see FIG. 8 for details).
Maximum temperature of sample surface: Up to 65.degree. C.
Black panel temperature: 63.+-.3.degree. C.
U.V. radiation intensity on sample surface: 100.+-.5
mW/cm.sup.2.
(3) Outdoor exposure
In Matsudo City, Chiba Pref., Japan, in January to December,
1985.
Properties Determined, and Methods of Determination
(1) Changes in color difference:
Color difference (.DELTA.E) was determined for every irradiation
unit time using a color difference meter, CR-100, product of
Minolta Camera Co., Ltd. and based on CIE 1976 L*a*b* color
space.
(2) Changes in gloss:
Using a gloss meter, Model GM-24, product of Murakami Color
Technique Lab. Co., Ltd., 60-deg specular gloss was measured.
Test Results
(1) Color difference changes in ABS sheet
Sample: ABS sheet, natural, 0.8 mm in thickness.
Reference color: Y=69.07, X=0.3343, y=0.3477.
Results: Given in FIG. 3 and Table 2.
FIG. 3 reveals that the prior-art tester achieved a nearly linear
change in .DELTA.E and that due to the influence of condensation,
the irradiation resulted in a reduced change in color difference in
the case of the tester of the invention. This result is in good
agreement with the result achieved by the outdoor exposure.
TABLE 2 ______________________________________ Prior-art Outdoor
Tester of Acceleration tester exposure invention ratio .DELTA.E
(hr) (month) (hr) (times) ______________________________________
5.0 2 0.15 4 27 15.0 10 0.50 17 21 20.0 17 1.60 30 38
______________________________________
The tester of the present invention achieved an average
acceleration ratio of 28.7 times. The acceleration ratio listed
above is expressed by: ##EQU1## wherein M is the number of months
during which the sample was exposed to the weather, and I is the
period (hours) of U.V. irradiation by the tester of the
invention.
(2) Gloss changes in ABS sheet
Sample: The same as above (1).
Results: Shown in FIG. 4 and Table 3.
FIG. 4 reveals no reduction in gloss achieved by the prior-art
tester, further indicating that a reduction occurred in 4 to 6
hours with the tester of the invention owing to the condensation
condition involved.
TABLE 3 ______________________________________ Prior-art Outdoor
Tester of Acceleration tester exposure invention ratio Gloss (hr)
(month) (hr) (month) ______________________________________ 80 --
3.7 18 148 60 -- 5.1 32 115 40 -- 5.7 47 87
______________________________________
The average acceleration ratio achieved was 116.7 times.
(3) Color difference changes in yellow PP sheet
Sample: Yellow PP sheet, 0.8 mm in thickness.
Reference color: Y=71.0, X=0.4413, y=0.4673.
Results: Given in FIG. 5 and Table 4.
FIG. 5 shows that the tester of the invention produced greater
changes in color difference than the prior-art tester and exhibited
nearly the same tendency as the outdoor exposure.
TABLE 4 ______________________________________ Prior-art Outdoor
Tester of Acceleration tester exposure invention ratio .DELTA.E
(hr) (month) (hr) (times) ______________________________________
3.0 120 0.5 45 8.0 6.0 -- 1.9 100 13.7 9.0 -- 5.3 190 20.1
______________________________________
The average acceleration ratio achieved was 13.9 times.
(4) Color difference changes in blue PP sheet
Sample: Blue PP sheet, 0.8 mm in thickness.
Reference color: Y=14.81, X=0.1880, y=0.1755.
Results: Given in FIG. 6 and Table 5.
FIG. 6 indicates that the tester of the invention achieved greater
acceleration than the prior-art tester but produced a result
slightly different from the result of outdoor exposure. The
difference appears attributable to a difference in the exposure
ratio between irradiation and water vapor condensate.
TABLE 5 ______________________________________ Prior-art Outdoor
Tester of Acceleration tester exposure invention ratio .DELTA.E
(hr) (month) (hr) (times) ______________________________________
3.0 75 1.6 20 57.6 6.0 100 4.0 50 57.6 10.0 140 8.0 85 67.8
______________________________________
The average acceleration ratio achieved was 61 times.
(5) Color difference changes in red PP sheet
Sample: Red PP sheet, 0.8 mm in thickness.
Reference color: Y=13.94, X=0.4989, y=0.3173.
Results: Given in FIG. 7 and Table 6.
FIG. 7 reveals that the tester of the invention attained less
acceleration than the prior-art tester but exhibited nearly the
same tendency as the outdoor weathering.
TABLE 6 ______________________________________ Prior-art Outdoor
Tester of Acceleration tester exposure invention ratio .DELTA.E
(hr) (month) (hr) (times) ______________________________________
3.0 25 3.1 75 29.8 6.0 55 7.2 120 43.2 8.0 80 10.0 150 48.0
______________________________________
The average acceleration ratio achieved was 40.3 times.
According to the invention described above, the sample can be
subjected to condensation of water vapor and can therefore be
tested for weather resistance under nearly natural conditions. In
spite of a large quantity of humid air supplied to the U.V.
irradiation compartment for causing condensation, the invention
precludes the cooling water jacket and the reflector surfaces from
fogging, assuring weathering tests or pretests therefor within a
very short period of time.
* * * * *